Hypertext Help with LaTeX

Math Formulas

All four of these environments are typeset in math
mode, using a math italic font and LaTeX
ideas about spacing in math mode. (See also math
fonts and styles.)

The math environment is for formulas that
appear right in the text. The displaymath, eqnarray, and equation
environments are for formulas that apppear on their own line(s).
The math environment can be used in both paragraph and LR mode, but
displaymath, eqnarray, and equation environments can be used only
in paragraph mode.